CARBOHYDRATES AS CONSTITUENTS OF PROTEINS

The first suggestion that carbohydrates may be components of all proteins was made by Claude Bernard, although the basis for this idea was an erroneous interpretation of experimental data. Early in the course of his brilliant studies on the physiology of glycogen, Bernard observed that the feeding of protein to dogs led to an increased deposition of glycogen in the livers of the experimental animals. As this work was done at a time when information regarding either the structure of proteins or the mode of synthesis of sugars in the organism or in the laboratory did not exist, Bernard assumed that the sugar molecule was preformed in the protein and postulated a glucosidic theory of protein structure. However, when the investigations of Lusk and his pupils demonstrated the synthesis of sugar from amino acids, the physiologic basis for the glucosidic structure of proteins disappeared. The presence of carbohydrates in proteins